When disrupting a mouse gene by knockout, why is it desirable to breed mice until offspring homozygous (−/−) for the knockout target gene are obtained?

Video transcript

Hi everyone. Let's look at our next question in knockout experiments, how do scientists ensure that the targeting vector has been properly introduced in the genome? So let's recall from our content video what knockout experiments are and that involves a technique to modify the genomic DNA of an organism, meaning that the changes then permanently preserved in its descendants. The change damages a specific gene in a way that makes it non functional. So you've knocked out a particular gene and can study the effects of what happens to the organism when that gene no longer produces its product. And this change is done by means of a targeting vector that allows you to damage that gene to find that gene in the entire genome and introduce a change that makes it non functional. But of course you want to know, have you managed to introduce this? Have you managed to make this change in the genome? And the way you can do that when we look at our answer choices is choice. See they put a selectable marker gene in a sequence inserted. So you have along when the sequence is inserted, you have a way of visually confirming visual confirmation that you've introduced the desired change. So this can be done with green fluorescent protein is a marker where your organisms glow green under ultraviolet light. In mice. It might be done by using a line where the pregnant surrogate mother is one color and the stem cells that were used that have the change are from mouse of another color? So you would actually visibly see in the offspring the fur color. You'd see a spotted pattern or other things like that. So again, you have a selectable marker gene. So you can visually see that your change gene has been introduced. All of our other answer choices here. So choice A. They wait for an organism's response. Choice be they test the presence of protein choice D. They monitor the transcription of an M. M. R. N. A. All of these are more labor intensive or take longer than just having this visual marker to tell you that you've successfully introduced your desired gene. So again, how do scientists ensure the targeting vector has been properly introduced in the genome in these knockout experiments? To A. C. They put a selectable marker gene in the sequence inserted. See you in the next video.